1. Field of the Invention
The present invention relates to a Multiple Input Multiple Output (MIMO) wireless communication system. More particularly, the present invention relates to an apparatus and method for detecting a signal in a MIMO wireless communication system.
2. Description of the Related Art
With the growing demand for high-speed, high-quality data transmission, a Multiple Input Multiple Output (MIMO) wireless communication system using a plurality of Transmit (Tx)/Receive (Rx) antennas has drawn attention as a technique capable of satisfying such a demand. In the MIMO technique, communication can be performed by using a plurality of streams through a plurality of antennas. Therefore, in comparison with the conventional technique using a single antenna, channel capacity can be significantly increased. For example, if a transmitting end and a receiving end use M Tx antennas and M Rx antennas, respectively, wherein a channel between the antennas is independent and a bandwidth and entire Tx power are fixed, then an average channel capacity is increased M times in comparison with the case of using the single antenna.
In a MIMO wireless communication system, signal detection schemes of the receiving end can be classified into linear schemes and non-linear schemes. Examples of linear schemes include a Zero Forcing (ZF) detection scheme and a Minimum Mean Squared Error (MMSE) detection scheme. Examples of non-linear schemes include a Vertical-Bell Laboratory Layered Space-Time (V-BLAST) detection scheme and a Maximum Likelihood (ML) detection scheme.
In the ZF detection scheme, a Tx signal is detected by multiplying an Rx signal vector and a detection matrix. When the ZF detection scheme is used, a noise amplification effect may occur. The MMSE detection scheme is used to solve the noise amplification effect. However, since the MMSE detection scheme is also a linear scheme, a performance limitation exists. The V-BLAST detection scheme outperforms the ZF detection scheme or the MMSE detection scheme in terms of detection performance. However, a recursive operation performed in the V-BLAST detection scheme results in a high complexity. Further, although the ML detection scheme shows an optimal detection performance, its implementation is difficult because its operational complexity exponentially increases in proportion to a constellation size.
As described above, various signal detection schemes proposed for a MIMO wireless communication system have trade-off relationships in terms of performance and complexity. Accordingly, in order for the MIMO wireless communication system to effectively detect a signal, there is a need for a signal detection scheme of which performance is close to that of the non-linear scheme and complexity is similar to that of the linear scheme.